Examine source code of play-with

{
  "description": "Play media on current URL in external application.",
  "manifest_version": 2,
  "name": "play-with",
  "version": "1.3.3resigned1",
  "default_locale": "en",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "play.js"
      ]
    }
  ],
  "permissions": [
    "activeTab",
    "contextMenus",
    "storage"
  ],
  "browser_action": {
    "browser_style": true,
    "default_title": "__MSG_actionName__",
    "default_icon": "icons/play-16.svg",
    "theme_icons": [
      {
        "light": "icons/play-16-light.svg",
        "dark": "icons/play-16-dark.svg",
        "size": 16
      }
    ]
  },
  "icons": {
    "16": "icons/play-16.svg"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{29607f9b-5198-4832-9ea9-16085d102734}"
    }
  }
}